Fall of South Vietnam

The Paris Peace Accords of January 27, 1973, were the beginning of the end of South Vietnam. There would be an immediate in-place permanent cease-fire. The U.S. agreed to withdraw all its troops in 60 days (but could continue to send military supplies); North Vietnam was allowed to keep its 200,000 troops in the South but was not allowed to send new ones.

Saigon had still not been able to create widespread popular support or run an effective administration. Its weaknesses were compounded by exaggerated confidence that the U.S. would return if and when needed.Although it was well-armed — its 2100 modern aircraft comprised the fourth largest air force in the world — the ARVN had never learned to fight large-scale operations against a conventional enemy.

Invasion and the fall of the south, 1975

In December 1974, the North Vietnamese Politburo gave command of the main assault to GEN Van Tien Dung, whose patron was Vo Nguyen Giap. Dung had been the chief of staff and head of logistics at Dien Bien Phu, and was considered a solid but not brilliant leader.

Preliminaries

In January, PAVN troops took and held their first objective, Phuoc Long, on January 6. Thieu told the cabinet that while it could be taken, it would not be worthwhile, although GEN Cao Van Vien, chief of the Joint General Staff, warned that it would encourage the North Vietnamese. The RVN Air Force had performed poorly there, losing 20 aircraft to groundfire yet not pressing in to hit targets accurately.

After this result, Le Duan personally told the Politburo that the next step should be to move against Darlac Province and its capital, Ban Me Thuot, and then toward the sea. From the Politburo meeting, Le Duc Tho took the idea to the senior military committee, where Vo Nguyen Giap joined the discussion, agreeing generally but wanting a deceptive move, as well, against Tai Nguyen. Dung left for his field headquarters on February 5.

North Vietnamese preparation

Dung's force had 18 divisions, with 300,000 of its 700,000, soldiers, conventionally organized with infantry, tanks and artillery.

The basic operational plan mirrored that which preceded the Battle of the Ia Drang: drive through Central Vietnam to the sea, cutting South vietnam in half. One important difference from 1966-7 was that the PAVN had mobile air defenses including anti-aircraft artillery and possibly surface-to-air missiles.

North invades South, 1975, using bases in Cambodia and Laos, and across DMZ

South Vietnamese defensive dispositions

The South Vietnamese military, however, had unclear goals, even on operational issues of when to trade territory for time. It had not learned to exercise command and control at the level of a national effort.

The initial southern strategy, issued by Nguyen Van Thieu, called "light at the top, heavy at the bottom", meaning that it would resist lightly, or abandon, the northern party of the country (I Corps), but stiffen resistance as the North extended. That was an attritional strategy, and the DRV had not broken under the much heavier attrition imposed by U.S. troops.

The ARVN, with 1.1 million soldiers, still had a 2-1 advantage in combat soldiers and 3-1 in artillery, but it misused its resources badly. Some ARVN units fought well; most collapsed under the 16-division onslaught. The North Vietnamese regular army, the PAVN, began a full-scale offensive by seizing Phuoc Long Province in January, 1975. In March, 1975, they continued their offensive campaigns by conducting diversionary attacks in the north threatening Pleiku and then attacking the lightly defended South Vietnamese rear area. Its air force, however, performed poorly, and often abandoned its bases.

First operational phase

Facing forces under Pham Van Phu, the PAVN feinted at Pleiku, as during the Ia Drang campaign, but sent their main, three-division attack at Ban Me Thuot, overwhelming it in a one-day battle on March 10.

Thieu ordered Phu to abandon Pleiku and Kontum and form a new defense line; Phu abandoned his command post, leaving approximately 200,000 refugees to move from the Central Highland to the coast. Phu committed suicide in Saigon when it fell on April 30.

Thieu then changed from the "light at the top" plan, demanding Hue be held to the last. The only road out of Hue, however, had been blocked by the PAVN.

Meanwhile, the PAVN hit attacked at multiple points along the seacoast, at Chu Lai, Quang Ngai, and threatening the major base at Da Nang.

Second Phase

The Politburo directed Dung to "liberate" the south before the monsoon season in May.

South Vietnamese appeals for U.S. support

President Thieu released written assurances, dated April 1973, from President Nixon that the U.S. would "react vigorously" if North Vietnam violated the truce agreement. But Nixon had resigned in August 1974 and his personal assurances were meaningless; After Nixon made the promises, Congress had prohibited the use of American forces in any combat role in Laos, Cambodia, and Vietnam without prior congressional approval. This was well known to the Saigon government. The Ford Administration, with specific legislative restrictions against direct aid and a lack of public support, was limited to some fnancial aid.

About 140,000 refugees managed to flee the country, chiefly by boat. The PAVN then concentrated its combat power to attack the six ARVN divisions isolated in the north. After destroying these divisions, the PAVN launched its "Ho Chi Minh Campaign" that with little fighting seized Saigon on April 30, ending the war.

No American military units had been involved until the final days, when Operation FREQUENT WIND was launched to protect the evacuation of Americans and 5600 senior Vietnamese government and military officials, and employees of the U.S. The 9th Marine Amphibious Brigade would enter Saigon to evacuate the last Americans from the American Embassy to ships of the Seventh Fleet.

Vietnam was unified under Communist rule, as nearly a million refugees escaped by boat. Saigon was renamed Ho Chi Minh City.